It is known to perform Single Ended Line Testing (SELT) in Digital Subscriber Lines (DSL). SELT comprises reflectometry-based measurement procedures that allow for determining a location of an impairment in a pair of conductors of a subscriber line. Typically, the impairment reflects a signal transmitted over the subscriber line. Thus, the location of a the impairment can be determined by measuring a signal propagation time from a single end of the subscriber line to the impairment and back to that single end of the DSL. However, SELT requires a special test signal be transmitted over the subscriber line and normal operation of the subscriber line must be interrupted during SELT. Therefore, SELT is not well-suited for repeated or automatic tests of the subscriber line.
Furthermore, DSL systems typically provide procedures for Dual Ended Line Testing (DELT). DELT is carried out by two nodes connected to the different end points of the DSL, e.g. by an access node and a node that is part of the Customer Premises Equipment (CPE). Results of the DELT can be retrieved from nodes at end points of the subscriber line by means, for instance, of the Simple Network Management Protocol (SNMP).